Method for estimating engine friction torque

• US 7,054,738 B1
• Filed: 10/17/2005
• Issued: 05/30/2006
• Est. Priority Date: 10/17/2005
• Status: Active Grant

• Current Assignee: Volvo Car Corporation (AB Volvo)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Stotsky, Alexander A
• Primary Examiner(s): Vo, Hieu T.
• Application Number:
  US11/252,286
• Time in Patent Office: 225 Days
• Field of Search: 701/115, 701/102, 701/110, 123/339.19, 123/339.22, 123/339.23, 123/339.24
• US Class Current: 701/115
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2200/1006 Engine torque losses, e.g. friction or pumping losses or losses caused by external loads of accessories
• CPC Class Codes: F02D 41/062 for starting F02D41/061 takes precedence
• CPC Class Codes: F02D 41/08 for idling F02D41/06, F02D41/16 take precedence
• CPC Class Codes: F02D 41/1402 Adaptive control
• CPC Class Codes: F02D 41/1497 With detection of the mechanical response of the engine
• CPC Class Codes: F02D 41/16 for idling
• CPC Class Codes: F02D 41/2422 Selective use of one or more tables

Abstract

Algorithms for real-time estimation of the engine friction torque in a vehicle powertrain are disclosed. Engine friction torque is estimated at start and at engine idle. Recursive and computationally efficient algorithms allow prediction of friction torque for a wide range of speeds and loads even with few new measured points by taking into account physical dependencies used for adaptation of the sites of the look-up tables (static maps). The algorithms make it possible to avoid drivability problems that could result from errors in estimating engine friction torque.

Claims

1. A method for estimating friction torque in an internal combustion engine having an electronic controller with repetitive control loops, the controller having memory storage registers that provide residence for a look-up table, the look-up table being characterized by at least two input variables, the method comprising the steps of:

determining a reference model of engine friction torque using calibrated engine friction torque data following an engine start event before engine idle is achieved;

determining a deviation of engine friction torque from the reference model to estimate actual friction torque; and

adapting sites in the look-up table if the estimated engine friction torque determined in a current engine start event differs from estimated engine friction torque determined in a preceding engine start event.

2. A method for estimating friction torque in an internal combustion engine having an electronic controller with repetitive control loops, the controller having memory storage registers that provide residence for a look-up table, the look-up table being characterized by at least an engine speed input variable and an indicated engine torque variable, the method comprising the steps of:

determining a reference model of engine friction torque using calibrated engine friction torque data following an engine start event before engine idle is achieved;

determining an estimated engine friction torque using current engine speed and indicated engine torque as variables;

determining a deviation of engine friction torque from the reference model based on the current engine speed and indicated engine torque variables; and

adapting sites in the look-up table if the estimated engine friction torque determined in a current engine start event differs from estimated engine friction torque determined in a preceding engine start event.

3. The method set forth in claim 2 wherein an adaptive algorithm for the look-up table comprises a recursive adaptation algorithm for sites in the look-up table, and adapting the sites in the look-up table by using two or more values of estimated engine friction torque at engine start and an additional value of estimated engine friction torque when engine idle is achieved.

4. The method set forth in claim 3 wherein the value of estimated engine friction torque at the time engine idle is achieved is modified and weighted in favor of idle friction torque by assigning different weights in the adaptation algorithm to estimated friction torque at engine idle and to estimated friction torque at engine start.

5. The method set forth in claim 4 wherein the look-up table defines a manifold for engine friction torque in three dimensional space with engine speed and indicated torque as independent variables, whereby the shape of the manifold reflects physical dependencies of the friction torque as a function of speed and indicated torque;

adaptation of the look-up table being associated with a motion of the manifold in three dimensional space, the position and the orientation of the manifold in three dimensional space thereby changing after adaptation, which in turn allows for a prediction of friction torque for a wide range of speeds and indicated torques even with few new measured points by taking into account physical dependencies present in the shape of the manifold, the adaptation algorithm being constructed so that only the sites of the look-up table are adapted, the values of engine friction torque between the sites being computed using interpolation.

6. The method set forth in claim 4 wherein the output of the look-up table is approximated using the polynomial:

7. The method set forth in claim 6 wherein parameter vectors are defined by minimizing a performance index using the equation:

8. The method set forth in claim 3 wherein the look-up table defines a manifold for engine friction torque in three dimensional space with engine speed and indicated torque as independent variables, whereby the shape of the manifold reflects physical dependencies of the friction torque as a function of speed and indicated torque;

adaptation of the look-up table being associated with a motion of the manifold in three dimensional space, the position and the orientation of the manifold in three dimensional space thereby changing after adaptation, which in turn allows for a prediction of friction torque for a wide range of speeds and indicated torques even with few new measured points by taking into account physical dependencies present in the shape of the manifold, the adaptation algorithm being constructed so that only the sites of the look-up table are adapted, the values of engine friction torque between the sites being computed using interpolation.

9. The method set forth in claim 8 wherein the parameter vector, which can be expressed as θ

ε

R⁽ⁿ⁺¹⁾², is updated for new measured data x_m, y_m and z_m with weight data w_m and divided into two parts, the first part, which remains unchanged, being expressed as θ

_cε

R<sup>(n+1)2−

q</sup> and the second part, which is adapted, being expressed as θ

_aε

R^q where q is the number of parameters to be adapted;

the two parts being expressed as;

θ

=[θ

_cθ

_a]^T and φ

=[φ

_cφ

_a]^T, where φ

_c is the part of a regressor corresponding to the parameter vector θ

_c and φ

_a is the part of the regressor corresponding to the parameter vector θ

_a;

adding the new measured data x_m, y_m and z_m to a new data set;

minimizing the following performance index;

10. The method set forth in claim 9 wherein the adaptive parameter θ

_a is computed recursively, the vector of the adaptive parameter being determined in accordance with the following equation at step (k−

1);

11. The method set forth in claim 10 including the step of cancelling an approximation error by computing the following differences {circumflex over (z)}_α

(h,p)−

{circumflex over (z)}_(h,p) between a polynomial approximation of the adapted table and a polynomial approximation of the original look-up table at every site h=1, . . . , D, p=1, . . . , G and adding to the values z_(h,p) of the original look-up table;

the values of the engine friction torque at the sites of the look-up table thereby being adapted in accordance with the equation;

z_f(h,p)=z_(h,p)+({circumflex over (z)}<sub>α

(h,p)</sub>−

{circumflex over (z)}_(h,p)), 

 

(23)

approximation errors present in {circumflex over (z)}<sub>α

(h,p)</sub> and {circumflex over (z)}_(h,p) due to usage of the difference {circumflex over (z)}<sub>α

(h,p)</sub>−

{circumflex over (z)}_(h,p) thereby being cancelled;

the values of friction torque between the sites being computed using interpolation.

12. A method for estimating friction torque in an internal combustion engine having an electronic controller with repetitive control loops, the controller having memory storage registers that provide residence for algorithms in the form of a look-up table, the look-up table being characterized by at least an engine speed input variable and an indicated engine torque variable, the method comprising the steps of:

measuring engine speed during an engine start event;

measuring engine speed during an engine idle state following an engine start event;

determining a reference model of engine friction torque using calibrated engine friction torque data based on indicated torque and measured engine speed at the time of an engine start event and an indicated torque and measured engine idle speed at the time engine idle is achieved;

determining an estimated engine friction torque during a time interval between an engine start event and the time engine idle is achieved using current engine speed and indicated engine torque variables;

determining a deviation of engine friction torque from the reference model based on current engine speed and indicated engine torque variables; and

adapting sites in the look-up table if the estimated engine friction torque determined in a current engine start event differs from estimated engine friction torque determined in a preceding engine start event.